DIÓXIDO DE CARBONO - (124-38-9)

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• "Atmospheric component used by photosynthetic plants to make carbohydrates and oxygen. The final oxidation product of all carbon-based fuels; its increase in the atmosphere is causing global warming. Used industrially as a refrigerant gas, a blanketing gas in fire extinguishers, and an effervescent gas in beverages. Combined with NH3 to form urea for fertilizers and plastics manufacture." 1

• "The carbon dioxide in the atmosphere controls the earth's surface temperature...the vibrational energy of some molecules is increased by the absorption of infrared radiation. Carbon dioxide and water absorb infrared radiation in this way. They absorb some of the infrared radiation emitted by the earth and prevent it from returning to space, thus keeping the temperatures of the troposphere and the earth's surface higher than they otherwise would be. It has been calculated that if there were no CO2 and H2O in the atmosphere, the average surface temperature of the earth would be -30ºC rather than +15ºC. The very high surface temperature of Venus is thought to be a result of the greenhouse effect exerted by its dense, carbon-dioxide-containing atmosphere." 3

• "21st most produced chemical in the United States in 1995 - 5.0 megatonnes." 4

• "Recarbonation [in chemical water analysis]" 5

• "It is present in the atmosphere (about 0.03 mole percent) and in our breath, where it results from the biological oxidation of food substances. The gas does have definite physiological effects if the air breathed contains greater than a few percent of CO2: It increases the rate of breathing, and air containing more than 5 mole percent can cause headache and unconsciousness if breathed for a sufficient length of time.

Carbon dioxide fire extinguishers contain carbon dioxide under pressure (mostly as a liquid); the carbon dioxide stream extinguishes a fire by displacing the air as well as by cooling the flame. It is a good, safe extinguisher for most fires.

The rising concentration of carbon dioxide in the atmosphere is a great concern, because of its role in the greenhouse effect. The principal gases in our atmosphere, O2 and N2, are transparent to visible light from the sun, absorbing only a portion of the ultraviolet radiation. When this sunlight reaches the surface of the earth, it is absorbed and converted to heat. The heat causes the atoms in the earth's surface to vibrate and radiate heat as infrared light. Neither O2 nor N2 absorbs infrared radiation, and if these were the only constituents of our atmosphere, this radiation would escape into outer space. However, other substances in the atmosphere, especially CO2, do absorb infrared radiation. This absorption warms the atmosphere, which then reradiates the infrared rays. The effect is to trap the sun's warmth.

The greenhouse effect is important on earth both in providing livable temperatures and in moderating the temperature fluctuations that otherwise would occur. On the moon, where there is no atmosphere, temperatures fluctuate from 100°C during the lunar day to -150°C at night. The concern of climatologists is that the additional greenhouse effect from the increase in carbon dioxide will drastically alter our present climate." 6

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